Gamma-secretase inhibitors

ABSTRACT

Compounds of formula I:  
                 
inhibit the processing of APP by gamma-secretase and hence find use in treatment of Alzheimer&#39;s disease.

The present invention relates to a novel class of compounds, their salts, pharmaceutical compositions comprising them, processes for making them and their use in therapy of the human body. In particular, the invention relates to novel cyclohexyl sulphonamides which inhibit the processing of APP by γ-secretase, and hence are useful in the treatment or prevention of Alzheimer's disease.

Alzheimer's disease (AD) is the most prevalent form of dementia. Although primarily a disease of the elderly, affecting up to 10% of the population over the age of 65, AD also affects significant numbers of younger patients with a genetic predisposition. It is a neurodegenerative disorder, clinically characterized by progressive loss of memory and cognitive function, and pathologically characterized by the deposition of extracellular proteinaceous plaques in the cortical and associative brain regions of sufferers. These plaques mainly comprise fibrillar aggregates of β-amyloid peptide (Aβ). The role of secretases, including the putative γ-secretase, in the processing of amyloid precursor protein (APP) to form Aβ is well documented in the literature and is reviewed, for example, in WO 01/70677.

There are various reports in the literature of compounds with inhibitory activity towards γ-secretase, as measured in cell-based assays. These are reviewed in WO 01/70677. Many of the relevant compounds are peptides or peptide derivatives.

WO 00/50391 discloses a broad class of sulphonamides as modulators of the production of β-amyloid, but neither discloses nor suggests the compounds of the present invention.

WO 02/081435 and WO 03/018543 disclose cyclohexyl sulphones having activity against γ-secretase, but neither disclose nor suggest the compounds of the present invention.

The present invention provides a novel class of cyclohexyl sulphonamides which are useful in the treatment or prevention of AD by inhibiting the processing of APP by γ-secretase, thus arresting the production of Aβ.

According to the invention, there is provided a compound of formula I:

wherein n is 0, 1, 2 or 3;

-   -   X represents H, halogen, CN, N₃, OH, OR¹, N(R²)₂, CO₂H, CO₂R¹,         OCOR¹, CHO, COR¹, CON(R²)₂, OCON(R²)₂, SCN, SR¹, S(O)R¹, SO₂R¹,         SO₂N(R²)₂, OSO₂N(R²)₂, NHCOR¹, NHCO₂R¹, NHCON(R²)₂, NHSO₂R¹ or         NHSO₂N(R²)₂;     -   R¹ represents CF₃ or C₁₋₆alkyl, C₂₋₆alkenyl, C₃₋₉cycloalkyl or         C₃₋₆cycloalkylC₁₋₆alkyl, any of which may bear up to 2         substituents selected from halogen, CN, CF₃, OR³, aryloxy, COR³,         CO₂R³, OCOR⁴, SO₂R⁴, N(R⁵)₂, and CON(R⁵)₂,     -   or R¹ represents aryl, arylC₁₋₆alkyl, C-heterocyclyl or         C-heterocyclylC₁₋₆alkyl;     -   each R² independently represents H or C₁₋₆alkyl, C₂₋₆alkenyl,         C₃₋₉cycloalkyl or C₃₋₆cycloalkylC₁₋₆alkyl, any of which may bear         up to 2 substituents selected from halogen, CN, CF₃, OR³, COR³,         CO₂R³, OCOR⁴, SO₂R⁴ and CON(R⁵)₂;     -   or two R² groups together with a nitrogen atom to which they are         mutually attached complete an N-heterocyclyl group;     -   R³ represents H or C₁₋₄alkyl;     -   R⁴ represents C₁₋₄alkyl;     -   R⁵ represents H or C₁₋₄alkyl, or two R⁵ groups together with a         nitrogen atom to which they are mutually attached complete an         azetidine, pyrrolidine, piperidine, morpholine, thiomorpholine         or thiomorpholine-1,1-dioxide ring;     -   each R⁶ independently represents H, C₁₋₆alkyl, C₃₋₆cycloalkyl or         C₂₋₆alkenyl, any of which is optionally substituted with up to 3         halogen atoms or with CN; or the two R⁶ groups and the nitrogen         to which they are attached complete an N-heterocyclyl group or a         heteroaryl group which is attached through N;     -   Ar² represents phenyl or heteroaryl, either of which bears 0-3         substituents independently selected from halogen, CN, NO₂, CF₃,         CHF₂, OH, OCF₃, CHO, CH═NOH, C₁₋₄alkoxy, C₁₋₄alkoxycarbonyl,         C₂₋₆acyl, C₂₋₆alkenyl and C₁₋₄alkyl which optionally bears a         substituent selected from halogen, CN, NO₂, CF₃, OH and         C₁₋₄alkoxy;     -   “aryl” at every occurrence thereof refers to phenyl or         heteroaryl which optionally bear up to 3 substituents selected         from halogen, CN, NO₂, CF₃, OCF₃, OH, COR³, CO₂R³, OCOR⁴,         N(R⁵)₂, CON(R⁵)₂ and optionally-substituted C₁₋₆alkyl,         C₁₋₆alkoxy, C₂₋₆alkenyl or C₂₋₆alkenyloxy wherein the         substituent is selected from halogen, CN, CF₃, phenyl, OR³,         CO₂R³, OCOR³a, N(R⁵)₂ and CON(R⁵)₂; and     -   “C-heterocyclyl” and “N-heterocyclyl” at every occurrence         thereof refer respectively to a heterocyclic ring system         attached through carbon or nitrogen, said ring system being         non-aromatic and comprising up to 10 atoms, at least one of         which is O, N or S, and optionally bearing up to 3 substituents         selected from oxo, halogen, CN, NO₂, CF₃, OCF₃, OR³, COR³,         CO₂R³, OCOR⁴, OSO₂R⁴, N(R⁵)₂, CON(R⁵)₂ and         optionally-substituted phenyl, C₁₋₆alkyl, C₁₋₆alkoxy,         C₂₋₆alkenyl or C₂₋₆alkenyloxy wherein the substituent is         selected from halogen, CN, CF₃, OR³, CO₂R³, OCOR⁴, N(R⁵)₂ and         CON(R⁵)₂;     -   or a pharmaceutically acceptable salt thereof.

Where a variable occurs more than once in formula I, the individual occurrences are independent of each other, unless otherwise indicated.

As used herein, the expression “C₁-_(x) alkyl” where x is an integer greater than 1 refers to straight-chained and branched alkyl groups wherein the number of constituent carbon atoms is in the range 1 to x. Particular alkyl groups include methyl, ethyl, n-propyl, isopropyl and t-butyl. Derived expressions such as “C₂₋₆alkenyl”, “hydroxyC₁₋₆alkyl”, “heteroarylC₁₋₆alkyl”, “C₂₋₆alkynyl” and “C₁₋₆alkoxy” are to be construed in an analogous manner.

The expression “C₃₋₉cycloalkyl” as used herein refers to nonaromatic monocyclic or fused bicyclic hydrocarbon ring systems comprising from 3 to 9 ring atoms. Examples include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cyclohexenyl and bicyclo[2.2.1]heptyl. Monocyclic systems of 3 to 6 members are preferred.

The expression “C₃₋₆ cycloalkylC₁₋₆alkyl” as used herein includes cyclopropylmethyl, cyclobutylmethyl, cyclopentylmethyl and cyclohexylmethyl.

The expression “heterocyclyl” as defined herein includes both monocyclic and fused bicyclic systems of up to 10 ring atoms selected from C, N, O and S. Mono- or bicyclic systems of up to 7 ring atoms are preferred, and monocyclic systems of 4, 5 or 6 ring atoms are most preferred. Examples of heterocyclic ring systems include azetidinyl, pyrrolidinyl, 3-pyrrolinyl, terahydrofuryl, 1,3-dioxolanyl, tetrahydrothiophenyl, tetrahydropyridinyl, piperidinyl, piperazinyl, morpholinyl, thiomorpholinyl, imidazolidinyl, oxazolidinyl, thiazolidinyl, 2,5-diazabicyclo[2.2.1]heptyl, 2-aza-5-oxabicyclo[2.2.1]heptyl and 1,4-dioxa-8-azaspiro[4.5]decanyl. Unless otherwise indicated, heterocyclyl groups may be attached through a ring carbon atom or a ring nitrogen atom where present. “C-heterocyclyl” indicates attachment through carbon, while “N-heterocyclyl” indicates attachment through nitrogen.

The expression “heteroaryl” as used herein means a monocyclic system of 5 or 6 ring atoms, or fused bicyclic system of up to 10 ring atoms, selected from C, N, O and S, wherein at least one of the constituent rings is aromatic and comprises at least one ring atom which is other than carbon. Monocyclic systems of 5 or 6 members are preferred. Examples of heteroaryl groups include pyridinyl, pyridazinyl, pyrimidinyl, pyrazinyl, pyrrolyl, furyl, thienyl, pyrazolyl, oxazolyl, isoxazolyl, thiazolyl, isothiazolyl, imidazolyl, oxadiazolyl, triazolyl and thiadiazolyl groups and benzo-fused analogues thereof. Further examples of heteroaryl groups include tetrazole, 1,2,4-triazine and 1,3,5-triazine. Pyridine rings may be in the N-oxide form. Heteroaryl groups are typically attached through carbon, but where the heteroaryl group comprises a 5-membered ring consisting of carbon and nitrogen atoms, attachment may alternatively be via nitrogen.

Where a phenyl group or heteroaryl group bears more than one substituent, preferably not more than one of said substituents is other than halogen or alkyl.

The term “halogen” as used herein includes fluorine, chlorine, bromine and iodine, of which fluorine and chlorine are preferred.

For use in medicine, the compounds of formula I may advantageously be in the form of pharmaceutically acceptable salts. Other salts may, however, be useful in the preparation of the compounds of formula I or of their pharmaceutically acceptable salts. Suitable pharmaceutically acceptable salts of the compounds of this invention include acid addition salts which may, for example, be formed by mixing a solution of the compound according to the invention with a solution of a pharmaceutically acceptable acid such as hydrochloric acid, sulphuric acid, benzenesulphonic acid, methanesulphonic acid, fumaric acid, maleic acid, succinic acid, acetic acid, benzoic acid, oxalic acid, citric acid, tartaric acid, carbonic acid or phosphoric acid. Alternatively, where the compound of the invention carries an acidic moiety, a pharmaceutically acceptable salt may be formed by neutralisation of said acidic moiety with a suitable base. Examples of pharmaceutically acceptable salts thus formed include alkali metal salts such as sodium or potassium salts; ammonium salts; alkaline earth metal salts such as calcium or magnesium salts; and salts formed with suitable organic bases, such as amine salts (including pyridinium salts) and quaternary ammonium salts.

Where the compounds according to the invention have at least one asymmetric centre, they may accordingly exist as enantiomers. Where the compounds according to the invention possess two or more asymmetric centres, they may additionally exist as diastereoisomers. It is to be understood that all such isomers and mixtures thereof in any proportion are encompassed within the scope of the present invention.

In formula I, n is 0, 1, 2 or 3, preferably 0, 1 or 2, most preferably 0 or 1.

X represents H, halogen, CN, N₃, OH, OR¹, N(R²)₂, CO₂H, CO₂R¹, OCOR¹, CHO, COR¹, CON(R²)₂, OCON(R²)₂, SCN, SR¹, S(O)R¹, SO₂R¹, SO₂N(R²)₂, OSO₂N(R²)₂, NHCOR¹, NHCO₂R¹, NHCON(R²)₂, NHSO₂R¹ or NHSO₂N(R²)₂. Preferred identities of X include CN, N₃, OH, CO₂H, CO₂R¹, CON(R²)₂, SO₂R¹, SO₂N(R²)₂, OSO₂N(R₂)₂, NHCOR¹, NHCO₂R¹, NHCON(R₂)₂, NHSO₂R¹ or NHSO₂N(R²)₂.

In one subset of the compounds of formula I, n is 1 or 2 and X represents CN, N₃, OH, CO₂H, CO₂R¹, CON(R²)₂, SO₂R¹, SO₂N(R²)₂ or OSO₂N(R²)₂. Within this subset, X preferably represents CO₂H, CO₂R¹, CON(R²)₂, SO₂R¹ or SO₂N(R²)₂.

In a second subset of the compounds of formula I, n is 0 and X represents NHCOR¹, NHCO₂R¹, NHCON(R²)₂, NHSO₂R¹ or NHSO₂N(R²)₂. Within this embodiment, X preferably represents NHSO₂R¹ or NHSO₂N(R²)₂, most preferably NHSO₂R¹.

R¹ is preferably CF₃, aryl or arylalkyl, or an alkyl, cycloalkyl or cycloalkylalkyl group, optionally substituted as described previously. Preferred substituents include halogen (especially fluorine or chlorine), CF₃, CN, OR³ (especially OH, OMe and OEt), COR³ (especially acetyl), CO₂R³ (especially CO₂H, CO₂Me and CO₂Et) and CON(R⁵)₂ (especially CONH₂).

Examples of alkyl groups represented by R¹ include methyl, ethyl, n-propyl, isopropyl, t-butyl, isobutyl, 2,2,2-trifluoroethyl, cyanomethyl, 2-hydroxyethyl, 2-methoxyethyl, 2-hydroxy-2-methylpropyl, carboxymethyl, ethoxycarbonylmethyl, 1-carboxyethyl, 1-ethoxycarbonylethyl, carbamoylmethyl and MeCOCH₂—.

Examples of cycloalkyl and cycloalkylalkyl groups represented by R¹ include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cyclopropylmethyl and cyclopentylmethyl.

When R¹ represents aryl or arylalkyl, the aryl group may be phenyl or heteroaryl, optionally substituted as defined previously. Preferred substituents include halogen (especially chlorine or fluorine), CF₃, OCF₃, alkyl (especially methyl), OH and alkoxy (especially methoxy). Preferred heteroaryl groups include pyridine, pyrimidine, fuiran, thiophene, thiazole, imidazole, triazole, thiadiazole and tetrazole.

Examples of aryl groups represented by R¹ include phenyl, 2-fluorophenyl, 4-fluorophenyl, 2,4-difluorophenyl, 2-chlorophenyl, 2-, 3- and 4-hydroxyphenyl, 2-trifluoromethoxyphenyl, 2-methoxyphenyl, 2-pyridyl (and the corresponding N-oxide), 4-pyridyl, 2-pyrimidinyl, 2-furyl, 2-thienyl, 2-thiazolyl, 2-imidazolyl, 2-methylfuran-3-yl, 4-methylthiazol-3-yl, 5-methyl-1,3,4-thiadiazol-2-yl, 1-methylimidazol-2-yl, 1-methyl-1,2,3,4-tetrazol-5-yl, 1,2,4-triazol-3-yl, 1-methyl-1,2,4-triazol-3-yl, 2-methyl-1,2,4-triazol-3-yl and 4-methyl-1,2,4-triazol-3-yl.

Arylalkyl groups represented by R¹ are typically optionally substituted benzyl, phenethyl, heteroarylmethyl or heteroarylethyl groups. Examples include benzyl, 2-furylmethyl, 2-thienylmethyl and 1-(2-thienyl)ethyl.

When X represents S(O)R¹, R¹ very aptly represents aryl, for example 2-pyridyl or 1-methyl-1,2,3,4-tetrazol-5-yl.

When X represents NHCO₂R¹, R¹ very aptly represents C₁₋₆alkyl (for example methyl) or arylalkyl (for example benzyl).

When X represents NHCOR¹, R¹ very aptly represents C₁₋₆alkyl (for example methyl) or substituted C₁₋₆alkyl (for example 2,2,2-trifluoroethyl or 1-hydroxy-2,2,2-trifluoroethyl).

For any N(R²)₂ fragment, preferably either at least one of the R² groups represents H or C₁₋₆alkyl such as methyl, or the two R² groups complete an N-heterocyclyl group.

When N(R²)₂ does not represent N-heterocyclyl, preferably one R² is H or methyl and the other is H or optionally substituted alkyl or cycloalkyl. Preferred substituents include CF₃, OR³ (such as OH and OMe), CO₂R³ (such as t-butoxycarbonyl) and OCOR⁴ (such as acetoxy). Within this embodiment, preferred identities for N(R²)₂ include NH2, NHMe, NHEt, NH^(i)Pr, NH^(t)Bu, NMe₂, NH-cyclobutyl, NHCH₂CF₃, NHCH₂CO₂ ^(t)Bu, NHCH₂CH₂OCOMe and NHCH₂CH₂OH.

When N(R²)₂ represents N-heterocyclyl, the heterocyclic ring is typically an optionally substituted azetidine, pyrrolidine, 3-pyrroline, piperidine, morpholine, thiomorpholine or 2-aza-5-oxabicyclo[2.2.1]heptane ring. Azetidine and pyrrolidine are preferred, and azetidine is particularly preferred. Preferred substituents include oxo, halogen (especially fluorine), CF₃, OR³ (especially OH), OCOR⁴ (especially acetoxy and trimethylacetoxy), OSO₂R⁴ (especially methanesulphonyloxy), CO₂R³ (especially CO₂H and CO₂Me), N(R⁵)₂ (especially dimethylamino) and alkyl (especially methyl). Examples of preferred N-heterocyclyl groups include azetidin-1-yl, pyrrolidin-1-yl, 3-pyrrolin-1-yl, piperidin-1-yl, morpholin-4-yl, thiomorpholin-4-yl, 2-aza-5-oxabicyclo[2.2.1]hept-2-yl, 3-oxo-azetidin-1-yl, 3-hydroxyazetidin-1-yl, 3acetoxyazetidin-1-yl, 3-(dimethylamino)azetidin-1-yl, 3-methanesulphonyloxyazetidin-1-yl, 3,3-difluoroazetidin-1-yl, 3-hydroxy-3-methylazetidin-1-yl, 2-carboxypyrrolidin-1-yl, 2-methoxycarbonylpyrrolidin-1-yl, 3-fluoropyrrolidin-1-yl, 3,3-difluoropyrrolidin-1-yl, 2-(trifluoromethyl)pyrrolidin-1-yl, 3-oxo-pyrrolidin-1-yl, 3-hydroxypyrrolidin-1-yl, 3-hydroxy-3-methylpyrrolidin-1-yl, 3-(trimethylacetoxy)pyrrolidin-1-yl, 4-(trifluoromethyl)piperidin-1-yl and 4,4-difluoropiperidin-1-yl.

When X represents NHCON(R²)₂, very aptly both R² groups represent methyl, or one R² represents H and the other represents C₁₋₆alkyl, such as methyl or ethyl.

The two R⁶ groups independently represent H, C₁₋₆alkyl, C₃₋₆cycloalkyl or C₂₋₆alkenyl, any of which is optionally substituted with up to 3 halogen atoms or with CN; or the two R⁶ groups and the nitrogen to which they are attached complete an N-heterocyclyl group or a heteroaryl group which is attached through N. Preferably, the two R⁶ groups do not both represent H. Examples of alkyl groups represented by R⁶ include methyl, ethyl, n-propyl, n-butyl. 3-methylbutyl, 3,3,3-trifluoropropyl and 4,4,4-trifluorobutyl. Examples of alkenyl groups represented by R⁶ include allyl, but-2-enyl and 3-methylbut-2-enyl.

When the two R⁶ groups complete an N-heterocyclyl group, said heterocyclic group typically comprises 4, 5, 6 or 7 ring atoms, preferably 5 or 6 ring atoms, and is optionally substituted as defined previously. Preferred rings include pyrrolidine, 3-pyrroline and piperidine. Preferred substituents include C₁₋₆alkyl (such as methyl), halogen (such as fluorine) and CF₃. Alternatively, the two R⁶ groups may complete an N-heteroaryl group such as pyrrol-1-yl, imidazol-1-yl, triazol-1-yl, tetrazol-1-yl or indol-1-yl, of which pyrrol-1-yl is preferred. Preferred examples of cyclic groups represented by N(R⁶)₂ include 4-fluoropiperidin-1-yl, 4,4-difluoropiperidin-1-yl, 4-(trifluoromethyl)piperidin-1-yl, pyrrolidin-1-yl, 3-pyrrolin-1-yl and pyrrol-1-yl, of which 4,4-difluoropiperidin-1-yl and 4-(trifluoromethyl)piperidin-1-yl are particularly preferred.

Ar² preferably represents optionally substituted phenyl, in particular phenyl bearing 2 or 3 substituents selected from halogen, CN, CF₃ and optionally-substituted alkyl. Ar² is typically selected from phenyl groups bearing halogen substituents (preferably fluorine) in the 2- and 5-positions or in the 2-, 3- and 6-positions, or from phenyl groups bearing a fluorine substituent in the 2-position and halogen, CN, methyl or hydroxymethyl in the 5-position. In a preferred embodiment of the invention, Ar² represents 2,5-difluorophenyl.

Examples of compounds in accordance with the invention include compounds of formula I in which Ar² represents 2,5-difluorophenyl and the other variables are as indicated in the following table: n X N(R⁶)₂ 0 NHSO₂CF₃ 4,4-di-F-piperidin-1-yl 0 NHSO₂CF₃ 4-CF₃-piperidin-1-yl 0 NHSO₂CF₃ diallylamino 0 NHSO₂CF₃ di(n-propyl)amino 0 NHSO₂CF₃ 3-pyrrolin-1-yl 0 NHSO₂CF₃ pyrrolidin-1-yl 0 NHSO₂CF₃ pyrrol-1-yl 0 NHSO₂CF₃ n-propylamino 0 NHSO₂CF₃ allylamino 0 NHSO₂CF₃ 3-methylbut-2-enylamino 0 NHSO₂CF₃ 3-methylbutylamino 0 NHSO₂CF₃ 4,4,4-trifluorobutylamino 0 NHSO₂CF₃ but-2-enylamino 0 H 4,4-di-F-piperidin-1-yl 0 H 4-CF₃-piperidin-1-yl 0 NHSO₂-(2-thienyl) 4-CF₃-piperidin-1-yl 1 CN 4,4-di-F-piperidin-1-yl 0 NHSO₂CF₃ 4-F-piperidin-1-yl 1 CONH₂ 4,4-di-F-piperidin-1-yl 1 CONHCH₂CH₂CF₃ 4,4-di-F-piperidin-1-yl 1 CONHCH₂CH₂F 4,4-di-F-piperidin-1-yl 0 NHSO₂CF₃ 3,3,3-trifluoropropylamino

The compounds of formula I have an activity as inhibitors of the processing of APP by γ-secretase.

The invention also provides pharmaceutical compositions comprising one or more compounds of formula I or the pharmaceutically acceptable salts thereof and a pharmaceutically acceptable carrier. Preferably these compositions are in unit dosage forms such as tablets, pills, capsules, powders, granules, sterile parenteral solutions or suspensions, metered aerosol or liquid sprays, drops, ampoules, transdermal patches, auto-injector devices or suppositories; for oral, parenteral, intranasal, sublingual or rectal administration, or for administration by inhalation or insufflation. For preparing solid compositions such as tablets, the principal active ingredient is mixed with a pharmaceutical carrier, e.g. conventional tableting ingredients such as corn starch, lactose, sucrose, sorbitol, talc, stearic acid, magnesium stearate, dicalcium phosphate or gums or surfactants such as sorbitan monooleate, polyethylene glycol, and other pharmaceutical diluents, e.g. water, to form a solid preformulation composition containing a homogeneous mixture of a compound of the present invention, or a pharmaceutically acceptable salt thereof. When referring to these preformulation compositions as homogeneous, it is meant that the active ingredient is dispersed evenly throughout the composition so that the composition may be readily subdivided into equally effective unit dosage forms such as tablets, pills and capsules. This solid preformulation composition is then subdivided into unit dosage forms of the type described above containing from 0.1 to about 500 mg of the active ingredient of the present invention. Typical unit dosage forms contain from 1 to 250 mg, for example 1, 2, 5, 10, 25, 50, 100, 200 or 250 mg, of the active ingredient. The tablets or pills of the novel composition can be coated or otherwise compounded to provide a dosage form affording the advantage of prolonged action. For example, the tablet or pill can comprise an inner dosage and an outer dosage component, the latter being in the form of an envelope over the former. The two components can be separated by an enteric layer which serves to resist disintegration in the stomach and permits the inner component to pass intact into the duodenum or to be delayed in release. A variety of materials can be used for such enteric layers or coatings, such materials including a number of polymeric acids and mixtures of polymeric acids with such materials as shellac, cetyl alcohol and cellulose acetate.

The liquid forms in which the novel compositions of the present invention may be incorporated for administration orally or by injection include aqueous solutions, suitably flavoured syrups, aqueous or oil suspensions, and flavoured emulsions with edible oils such as cottonseed oil, sesame oil or coconut oil, as well as elixirs and similar pharmaceutical vehicles. Suitable dispersing or suspending agents for aqueous suspensions include synthetic and natural gums such as tragacanth, acacia, alginate, dextran, sodium carboxymethylcellulose, methylcellulose, poly(vinylpyrrolidone) or gelatin.

The present invention also provides a compound of formula I or a pharmaceutically acceptable salt thereof for use in a method of treatment of the human body. Preferably the treatment is for a condition associated with the deposition of β-amyloid. Preferably the condition is a neurological disease having associated β-amyloid deposition such as Alzheimer's disease.

The present invention further provides the use of a compound of formula I or a pharmaceutically acceptable salt thereof in the manufacture of a medicament for treating or preventing Alzheimer's disease.

The present invention further provides a method of treatment of a subject suffering from or prone to a condition associated with the deposition of β-amyloid which comprises administering to that subject an effective amount of a compound according to formula I or a pharmaceutically acceptable salt thereof. Preferably the condition is a neurological disease having associated β-amyloid deposition such as Alzheimer's disease.

For treating or preventing Alzheimer's Disease, a suitable dosage level is about 0.01 to 250 mg/Kg per day, preferably about 0.10 to 100 mg/Kg per day, especially about 1.0 to 50 mg/Kg, and for example about 10 to 30 mg/Kg of body weight per day. Thus, a dose of about 500 mg per person per day may be considered. The compounds may be administered on a regimen of 1 to 4 times per day. In some cases, however, dosage outside these limits may be used.

Compounds of formula I in which X represents CN, N₃, OR¹, N(R²)₂, SCN, SR¹ or SO₂R¹ may be prepared by reaction of, respectively, MCN, MN₃, MOR¹, HN(R²)₂, MSCN, MSR¹ or MSO₂R¹ with a compound of formula (1):

where M is a metal cation (preferably an alkali metal cation, such as Li or Na), G is a leaving group, R¹, R⁶, Ar², and n have the same meanings as before, and bond a is cis with respect to (R⁶)₂NSO₂ when n is 1, 2 or 3 and trans when n is 0. Suitable identities for G include halide (especially bromide or iodide) and alkyl- or arylsulphonate. Iodide and mesylate are particularly suitable. The metallated derivatives MOR¹¹, MSR¹ and MSO₂R¹ may be generated by reaction of the corresponding hydrides with NaOH, LiOH, NaH, BuLi, LiN(^(i)Pr)₂ or similar, and are typically reacted in situ with the compounds (1).

Compounds of formula I in which X represents S(O)R¹ may be prepared from the corresponding compounds in which X represents SR¹ by oxidation with one equivalent of m-chloroperoxybenzoic acid. The oxidation takes place at ambient temperature in a dichloromethane-water mixture. Oxidation of the same compounds with two equivalents of m-chloroperoxybenzoic acid, or with sodium periodate in the presence of RuO₂ catalyst, provides an alternative route to compounds in which X represents SO₂R¹.

Compounds of formula I in which X represents SO₂N(R²)₂ may be prepared by reaction of (R²)₂NH with a sulphonyl chloride of formula (2):

where R², R⁶, Ar² and n have the same meanings as before. The reaction is typically carried out in dichloromethane at ambient temperature, either using excess of the amine or using an additional base such as potassium carbonate, pyridine or triethylamine.

Compounds of formula I in which X represents OSO₂N(R²)₂ may be prepared by reaction of a sulphamoyl chloride (R²)₂NSO₂Cl with an alcohol of formula (3):

where R², R⁶, Ar² and n have the same meanings as before. The reaction is typically carried out in dichloromethane at ambient temperature in the presence of a base such as pyridine or triethylamine. The sulphamoyl chlorides (R²)₂NSO₂Cl are available by reaction of (R²)²NE with sulphuryl chloride in acetonitrile at ambient temperature.

Compounds of formula I in which X represents NHCOR¹, NHCO₂R¹, NHSO₂R¹ or NHSO₂N(R²)₂ may be prepared by reacting an amine of formula (4) with, respectively, R¹COCl, R¹OCOCl, R¹SO₂Cl and (R²)₂NSO₂Cl:

where R¹, R⁶, Ar² and n have the same meanings as before. The reaction is typically carried out in dichloromethane at ambient or reduced temperature, in the presence of a base such as pyridine or triethylamine. Alternatively, the compounds in which X represents NHCOR¹ may be prepared by coupling of amines (4) with R¹CO₂H. Any of the standard peptide coupling procedures may be used, for example the use of 1-hydroxybenzotriazole or dimethylaminopyridine and 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide.

An alternative route to the compounds of formula I in which X represents NHSO₂N(R²)₂ involves reacting an amine of formula (4) with catechol sulphate and reacting the resulting sulphamate with (R²)₂NH. The first step is typically carried out in THF at 0° C., and the second step at 80° C. in dioxan.

Compounds of formula I in which X represents NHCON(R²)₂ may be prepared by treating an carboxylic acid of formula (5) first with diphenylphosphoryl azide, and then with (R²)₂NH:

where R², R⁶, Ar² and n have the same meanings as before. The first step is typically carried out in toluene at 110° C. in the presence of triethylamine, and the second step at ambient temperature in the same solvent.

Compounds of formula I in which X represents COR¹ may be prepared by reaction of a compound of formula (6a) with R¹-M¹:

where M¹ represents Li or MgBr and R⁶, Ar² and n have the same meanings as before. The reaction is typically carried out in THF or diethyl ether at reduced temperature. When M¹ is MgBr, R¹ preferably represents substituted phenyl.

The compounds of formulae (3), (4), (5) and (6b) are themselves compounds in accordance with the invention.

The compounds of formula (1) in which G is iodide may be obtained by reaction of the corresponding compounds of formula (5) with iodosobenzene diacetate and iodine under irradiation. The compounds of formula (1) in which G is alkyl- or arylsulphonate are available from the reaction of the corresponding compounds of formula (3) (or, when n is zero, the trans isomers thereof) with the appropriate sulphonyl chloride.

The sulphonyl chlorides of formula (2) may be obtained by reaction of the compounds of formula (1) with potassium thioacetate, hydrolysis of the resulting thioester to give the corresponding thiol, then treatment of the thiol with potassium nitrate and sulphuryl chloride.

The alcohols of formula (3) in which n is 1, 2 or 3 are available by reduction of the acids of formula (5), the value of n increasing by 1 in the process. The alcohols of formula (3) in which n is 0 are available from the reduction of the cyclohexanones of formula (7).

where R⁶ and Ar² have the same meanings as before. Reduction with L-Selectride™ provides the cis isomer selectively. Reduction with sodium borohydride provides a mixture of cis and trans isomers which may be separated by chromatography.

The amines of formula (4) are available from the carboxylic acids (5) by sequential reaction with oxalyl chloride, sodium azide and benzyl alcohol, followed by hydrolysis of the resulting carbamate. Alternatively, they may be obtained from the mesylates of the alcohols (3) (or, when n is zero, the trans isomers thereof) by displacement with azide ion, followed by reduction.

The carboxylic acids of formula (5) in which n is 0 are available from the trans isomers of the alcohols (3) in which n is 0 by formation of the mesylate ester, followed by nucleophilic displacement with cyanide ion and hydrolysis of the resulting nitrile. The corresponding acids in which n is 1 are formed by condensation of cyclohexanones (7) with ethyl (diethoxyphosphinyl)acetate, followed by reduction of the resulting alkenyl ester (i.e. (6b)) and hydrolysis of the ester group. The corresponding acids in which n is 2 or 3 are obtainable by standard methods of homologation. For example, reduction of an acid (5) in which n is 1 provides an alcohol (3) in which n is 2, and mesylation, displacement with cyanide, and hydrolysis provides the corresponding acid in which n is 2. Repeating this process provides the acid (5) in which n is 3.

The N-methoxyamides (6a) are obtained from the corresponding carboxylic acids by treatment first with oxalyl chloride and then with N,O-dimethylhydroxylamine.

Cyclohexanones (7) are available from the alkylation of Ar²CH₂SO₂N(R⁶)₂ (8) with bis(iodides) (9), followed by hydrolysis of the ketal group:

where R⁶ and Ar² have the same meanings as before. The alkylation takes place in DMF in the presence of sodium hydride, and the hydrolysis may be carried out in aqueous acetic acid in the presence of p-toluenesulphonic acid.

The sulphonamides (8) are availble from the reaction of sulphonyl chlorides Ar²CH₂SO₂Cl (10) with (R⁶)₂NH, where R⁶ and Ar² have the same meanings as before. The reaction takes place in an inert solvent such as dichloromethane in the presence of a base such as triethylamine.

It will be apparent to those skilled in the art that individual compounds of formula I prepared by the above routes may be converted into other compounds in accordance with formula I by means of well known synthetic techniques such as alkylation, esterification, amide coupling, hydrolysis, oxidation and reduction. Such techniques may likewise be carried out on precursors of the compounds of formula I. For example, a compound of formula I in which X is SCN may be treated with trimethyl(trifluoromethyl)silane and tetrabutylammonium fluoride to provide the corresponding compound in which X is SCF₃, which in turn may be oxidised to the corresponding compound wherein X is SO₂CF₃.

Also, substituents on the aromatic group Ar² may be added or interconverted by means of standard synthetic processes carried out on the compounds of formula I or their precursors. For example, in esters (6b) a chlorine or bromine atom on Ar² may be replaced by vinyl by treatment with vinyltributyltin in the presence of tri-t-butylphosphine, cesium fluoride and tris(dibenzylideneacetone)dipalladium(0). Ozonolysis of the vinyl group provides the corresponding formyl derivative, which may be transformed in a variety of ways, including oxidation to the corresponding acid, reduction to the corresponding benzyl alcohol, and conversion to the corresponding nitrile by treatment with hydroxylamine then triphenylphosphine and carbon tetrachloride.

Similarly, the R⁶ groups in compounds of formula I may be interconverted using standard techniques. For example, alkenyl groups represented by R⁶ may be hydrogenated to provide the corresponding alkyl derivatives. Allyl groups represented by R⁶ may be replaced with H by treatment with zirconocene dichloride or with diisobutylaluminium hydride and NiCl₂. Alternatively, compounds in which both R⁶ groups are allyl may be converted to the corresponding 3-pyrrolin-1-yl derivatives by treatment with Grubbs catalyst, and then to the corresponding pyrrolidin-1-yl derivatives by hydrogenation or to the pyrrol-1-yl derivatives by oxidation. Compounds in which one or both R⁶ groups represent H may be alkylated in conventional manner. Detailed procedures for such transformations are provided in the Examples section.

Where they are not themselves commercially available, the starting materials and reagents employed in the above-described synthetic schemes may be obtained by the application of standard techniques of organic synthesis to commercially available materials.

It will be appreciated that many of the above-described synthetic schemes may give rise to mixtures of stereoisomers. Such mixtures may be separated by conventional means such as fractional crystallisation and preparative chromatography.

Certain compounds according to the invention may exist as optical isomers due to the presence of one or more chiral centres or because of the overall asymmetry of the molecule. Such compounds may be prepared in racemic form, or individual enantiomers may be prepared either by enantiospecific synthesis or by resolution. The novel compounds may, for example, be resolved into their component enantiomers by standard techniques such as preparative HPLC, or the formation of diastereomeric pairs by salt formation with an optically active acid, such as (−)-di-p-toluoyl-d-tartaric acid and/or (+)-di-p-toluoyl-1-tartaric acid, followed by fractional crystallisation and regeneration of the free base. The novel compounds may also be resolved by formation of diastereomeric esters or amides, followed by chromatographic separation and removal of the chiral auxiliary.

During any of the above synthetic sequences it may be necessary and/or desirable to protect sensitive or reactive groups on any of the molecules concerned. This may be achieved by means of conventional protecting groups, such as those described in Protective Groups in Organic Chemistry, ed. J. F. W. McOmie, Plenum Press, 1973; and T. W. Greene & P. G. M. Wuts, Protective Groups in Organic Synthesis, John Wiley & Sons, 3^(rd) ed., 1999. The protecting groups may be removed at a convenient subsequent stage using methods known from the art.

An assay which can be used to determine the level of activity of compounds of the present invention is described in WO01/70677. A preferred assay to determine such activity is as follows:

-   -   1) SH-SY5Y cells stably overexpressing the βAPP C-terminal         fragment SPA4CT, are cultured at 50-70% confluency. 10 mM sodium         butyrate is added 4 hours prior to plating.     -   2) Cells are plated in 96-well plates at 35,000 cells/well/100         μL in Dulbecco's minimal essential medium (DMEM) (phenol         red-free) +10% foetal bovine serum (FBS), 50 mM HEPES buffer         (pH7.3), 1% glutamine.     -   3) Make dilutions of the compound plate. Dilute stock solution         18.2× to 5.5% DMSO and 11× final compound concentration. Mix         compounds vigorously and store at 4° C. until use.     -   4) Add 10 μL compound/well, gently mix and leave for 18 h at 37°         C., 5% CO₂.     -   5) Prepare reagents necessary to determine amyloid peptide         levels, for example by Homogeneous Time Resolved Fluorescence         (HTRF) assay.     -   6) Plate 160 μL aliquots of HTRF reagent mixture to each well of         a black 96-well HTRF plate.     -   7) Transfer 40 μL conditioned supernatant from cell plate to         HTRF plate. Mix and store at 4° C. for 18 hours.     -   8) To determine if compounds are cytotoxic following compound         administration, cell viability is assessed by the use of redox         dye reduction. A typical example is a combination of redox dye         MTS (Promega) and the electron coupling reagent PES. This         mixture is made up according to the manufacturer's instructions         and left at room temperature.     -   9) Add 10 μL/well MTS/PES solution to the cells; mix and leave         at 37° C.     -   10) Read plate when the absorbance values are approximately         0.4-0.8. (Mix briefly before reading to disperse the reduced         formazan product).     -   11) Quantitate amyloid beta 40 peptide using an HTRF plate         reader.         -   Alternative assays are described in Biochemistry, 2000,             39(30), 8698-8704.         -   See also, J. Neuroscience Methods, 2000, 102, 61-68.

The Examples of the present invention all had an ED₅₀ of less than 1 μM, typically less than 0.5 μM, in most cases less than 100 nM, and in preferred cases less than 10 nM, in at least one of the above assays.

The following examples illustrate the present invention.

EXAMPLES Example 1 N-[cis-4-(2,5-difluorophenyl)-4-(4-fluoropiperidine-1-sulfonyl)cyclohexyl]-1,1,1-trifluoromethanesulfonamide

Step, 1 1-(2,5-difluorophenylmethanesulfonyl)-4-fluoropiperidine

4-Fluoropiperidine.HBr (5 g, 27.3 mmol) in dichloromethane (50 ml) was cooled to 0° C. and treated with triethylamine (3.8 ml, 68.3 mmol), then 2,5-difluorophenylmethane sulfonyl chloride (6.2 g, 27.3 mmol) in dichloromethane (50 ml) was added dropwise. The reaction mixture was left to stir at room temperature overnight, then quenched (0.1 N citric acid) and extracted (ethyl acetate). The organic phase was washed (brine), dried (magnesium sulfate) and evaporated in vacuo. The crude product was chromatographed on silica, eluting with 20-30% ethyl acetate/isohexane to give the title product. (3.87 g, 48%).

¹H NMR (500 MHz, CDCl₃) δ 1.75-1.90 (4H, m), 3.15-3.22 (2H, m), 3.30-3.36 (2H), m), 4.24 (2H, s), 4.73-4.76 (0.5H, m), 4.85-4.88 (0.5H, m), 7.03-7.12 (2H, m), 7.22-7.25 (1H, m).

Step 2 1-8-(2,5-difluorophenyl)-1,4-dioxa-spiro[4.5]decane-8-sulfonyl]-4-fluoropiperidine

To the product of Step 1 (3.87 g, 13.2 mmol) in dimethylformamide (50 ml) at room temperature was added 2,2-bis(2-iodoethyl)-[1,3]-dioxolane (5.55 g, 14.5 mmol) followed (portionwise) by sodium hydride (1.16 g, 60% w/w in mineral oil, 29.1 mmol). After stirring at room temperature overnight the mixture was quenched (water) and extracted (ethyl acetate). The organic phase was washed (water, brine), dried (magnesium sulfate) and evaporated in vacuo. The crude material was chromatographed on silica, eluting with 10-20% ethyl acetate/isohexane to give the title compound (2.99 g, 54%).

¹H NMR (500 MHz, CDCl₃) δ 1.47 (2H, td, J=3.4 and 13.9 Hz), 1.70-1.85 (6H, m), 2.38 (2H, t, J=13.7 Hz), 2.77 (2H, bs), 2.96-3.38 (4H, vbs), 3.89-3.91 (2H, m), 3.94-3.97 (2H, m), 4.71-4.90 (1H, m), 7.05-7.08 (2H, m), 7.23-7.25 (1H, m).

Step 3 4-(2,5-difluorophenyl)-4-(4-fluoropiperidine-1-sulfonyl)-cyclohexanone

The product of Step 2 (2.99 g, 7.14 mmol) and p-toluenesulfonic acid (1.62 g, 8.56 mmol) in acetic acid/water (40 ml/10 ml) were heated at 50° C. for 3 hours and then diluted (water) and extracted (diethyl ether). The organic phase was washed (saturated sodium hydrogen carbonate, brine), dried (magnesium sulfate) and evaporated in vacuo. The crude product was azeotroped with toluene, followed by ethyl acetate, followed by dichloromethane. The crude product then was chromatographed on silica, eluting with 30% ethyl acetate/isohexane to give the cyclohexanone (1.7 g, 64%).

¹H NMR (500 MHz, CDCl₃) δ 1.71-1.89 (4H, m), 2.19-2.28 (2H, m), 2.47-2.55 (4H, m), 3.04-3.40 (6H, m), 4.75-4.95 (1H, m), 7.14-7.17 (2H, m), 7.31-7.36 (1H, m).

Step 4 trans-4-(2,5-difluorophenyl)-4-(4-fluoropiperidine-1-sulfonyl)-cyclohexanol

The cyclohexanone (1.7 g, 4.53 mmol) in ethanol/tetrahydrofuran (30 ml/5 ml) was cooled to −78° C. Sodium borohydride (0.34 g, 9.07 mmol) was added portionwise. After stirring for 2 hours at −78° C., the mixture was quenched at −78° C. (0.1 N citric acid), allowed to warm to room temperature and extracted (ethyl acetate). The organic phase was washed (water, brine), dried (magnesium sulfate) and evaporated in vacuo to give the crude alcohol (1.56 g, 91%).

¹H NMR (500 MHz, CDCl₃) δ 1.19-1.27 (2H, m), 1.43-1.64 (2H, m), 1.70-1.85 (4H, m), 1.97-2.03 (1H, m), 2.12 (2H, t, J=13.8 Hz), 2.65-3.33 (6H, m), 3.73-3.78 (1H, m), 4.71-4.89 (1H, m), 7.06-7.10 (2H, m), 7.23-7.27 (1H, m).

Step 5 cis-4-(2,5-difluorophenyl)-4-(4-fluoropiperidine-1-sulfonyl)-cyclohexylamine

The alcohol (1.56 g, 4.14 mmol) in dichloromethane (30 ml) at −10° C. was treated with triethylamine (0.98 ml, 7.03 mmol), followed by methanesulfonyl chloride (0.48 ml, 6.21 mmol). The mixture was stirred at room temperature for 1.5 hours then diluted (dichloromethane) Extractive work-up afforded the crude mesylate. (1.80 g, 96%). Sodium azide (0.39 g, 5.93 mmol) was added to a solution of the mesylate (1.80 g, 3.96 mmol) in N,N-dimethylformamide (40 ml) and heated at 95° C. for 2 hours. Further sodium azide (0.13 g, 1.99 mmol) was added and the mixture was stirred for 4 hours, then quenched (water) and extracted (ethyl acetate). The organic phase was washed (water, brine), dried (magnesium sulfate) and evaporated in vacuo to give crude azide(1.37 g, 86%).

The azide (1.37 g, 3.41 mmol) and triphenylphosphine (1.79 g, 6.82 mmol) in tetrahydrofuran/water (30 ml/3 ml) were refluxed overnight, then quenched (water) and extracted (ethyl acetate/isohexane). The organic phase was washed (water, brine), dried (magnesium sulfate) and evaporated in vacuo. The crude product was chromatographed on silica, eluting with 5% ammonia in methanol (2.0 N)/dichloromethane to give the title amine. (0.76 g, 59%).

¹H NMR (400 MHz, CDCl₃) δ 1.38 (2H, s), 1.51-1.58 (2H, m), 1.61-1.70 (2H, m), 1.75-1.88 (4H, m), 2.46-2.57 (4H, m), 2.68-3.30 (5H, m), 4.70-4.91 (1H, m), 7.04-7.08 (2H, m), 7.23-7.28 (1H, m).

Step 6 N-[cis-4-(2,5-difluorophenyl)-4-(4-fluoropiperidine-1-sulfonyl)cyclohexyl]-1,1,1-trifluoromethanesulfonamide

The amine (0.20 g, 0.53 mmol) in dichloromethane (15 ml) was treated with triethylamine (0.07 ml, 0.53 mmol), cooled to −78° C. and trifluoromethanesulfonic anhydride (0.18 ml, 1.06 ml) was added dropwise. The mixture was stirred for 3 hours at −78° C. then quenched (0.1 N citric acid) and extracted (dichloromethane). The organic phase was washed (water, brine), dried (magnesium sulfate) and evaporated in vacuo. The crude product was chromatographed on silica, eluting with 20% ethyl actetate/isohexane to give the title compound (0.17 g, 64%).

¹H NMR (400 MHz, CDCl₃) δ 1.63-170 (2H, s), 1.71-190 (4H, m), 1.95-2.03 (2H, m), 2.37 (2H, t, J=13.0 Hz), 2.61-2.73 (2H, m), 2.85-3.34 (4H, m), 3.77-3.80 (1H, m), 4.68-4.92 (1H, m), 5.72 (1H, d, J=8.2 Hz), 7.09-7.12 (2H, m), 7.21-7.25 (1H, m).

Example 2 N-[cis-4-(2,5-difluorophenyl)-4-(4-trifluoromethylpiperidne-1-sulfonyl)-cyclohexyl]-1,1,1-trifluoromethanesulfonamide

Prepared as described in Example 1, substituting 4-trifluoromethylpiperidine for 4-fluoropiperidine in Step 1.

¹H NMR (500 MHz, CDCl₃) δ 1.45-1.58 (2H, bs), 1.61-1.70 (2H, m), 1.74-1.77 (2H, m), 1.99-2.02 (2H, m), 2.04-2.13 (1H, bs), 2.38 (2H, t, J=13.3 Hz), 2.57-2.75 (4H, bs), 3.28-3.65 (2H, vbs), 3.75-3.82 (1H, m), 5.65-5.72 (1H, bs), 7.08-7.12 (2H, m), 7.22-7.24 (2H, m).

Example 3 N-[cis-4-(2,5-difluorophenyl)-4-(4,4-difluoropiperidine-1-sulfonyl)cyclohexyl]-1,1,1-trifluoromethanesulfonamide

Prepared as described in Example 1, substituting 4,4-difluoropiperidine for 4-fluoropiperidine in Step 1.

Example 4

Thiophene-2-sulfonic acid cis-[4-(2,5-difluorophenyl)-4-(4-trifluoromethyl-piperidine-1-sulfonyl)cyclohexyl]-amide

Prepared as for Example 2, carrying out the final step at ambient temperature using thiophene-2-sulfonyl chloride in place of trifluoromethanesulfonic anhydride.

¹H NMR (400 MHz, CDCl₃) δ 1.44-1.53 (4H, m), 1.73-1.84 (4H, m), 2.05-2.14 (1H, m), 2.29 (2H, t, J=13.4 Hz), 2.53-2.75 (4H, m), 3.46-3.54 (3H, m), 5.00 (1H, d, J=6.6 Hz), 7.03-7.09 (3H, m), 7.17-7.21 (1H, m), 7.58-7.62 (2H, m).

Example 5 cis-N,N-diallyl-1-(2,5-difluorophenyl)-4-{[(trifluoromethyl)sulfonyl]amino}cyclohexanesulfonamide

Prepared by the procedure of Example 1, using diallylamine in Step 1.

¹H NMR (500 MHz, CDCl₃) 7.26-7.22 (1H, m), 7.11-7.08 (2H, m), 6.05 (1H, brs), 5.65-5.62 (2H, m), 5.19-5.08 (4H, m), 3.79 (1H, brm), 3.48 (4H, brs), 2.75 (2H, vbrs), 2.38 (2H, appt), 2.05-1.98 (2H, m), 1.68-1.62 (2H, m).

Example 6 cis-1-(2,5-difluorophenyl)-N,N-dipropyl-4-{[(trifluoromethyl)sulfonyl]amino}cyclohexanesulfonamide

A solution of the product of Example 5 (70 mg) and 5% Pd—C (30 mg) in ethyl acetate (5 ml) was hydrogenated at 50 psi for 2 h. The catalyst was removed by filtration and the organic solvent was removed by evaporation under reduced pressure to give the title compound (65 mg, 100%) as a white solid.

Example 7 N-[cis-4-(2,5-difluorophenyl)-4-(2,5-dihydro-1H-pyrrol-1-ylsulfonyl)cyclohexyl]-1,1,1-trifluoromethanesulfonamide

A solution of the product of Example 5 (320 mg) in dichloromethane (70 ml) was treated with 1,3-bis-(2,4,6-trimethylphenyl)-2-imidazolidinylidene)dichloro(phenylmethylene)-(tricyclohexylphosphine)ruthenium (5 mg) and stirred at room temperature overnight. The reaction mixture was evaporated in vacuo and purified by flash column chromatography to give the title product (300 mg, 99%) as a white solid. ¹H NMR (500 MHz, CDCl₃) 7.27-7.23 (1H, m), 7.11-7.04 (2H, m), 5.83 (1H, s), 5.64 (2H, s), 3.91 (4H, vbrs), 3.79 (1H, brs), 2.72 (2H, appd), 2.44 (2H, appt), 2.02-1.99 (2H, m), 1.72-1.65 (2H, m).

Example 8 N-[cis-4-(2,5-difluorophenyl)-4-(pyrrolidin-1-ylsulfonyl)cyclohexyl]-1,1,1-trifluoromethanesulfonamide

The product of Example 7 (65 mg) and 5% Pd—C (30 mg) in ethyl acetate (5 ml) was hydrogenated at 50 psi for 2 h. The catalyst was removed by filtration and the organic solvent was removed by evaporation under reduced pressure to give the title compound (65 mg, 100%) as a white solid. ¹H NMR (500 MHz, CDCl₃) 7.26-7.23 (1H, m), 7.11-7.04 (2H, m), 6.30 (1H, d, J=8.2), 3.79-3.77 (1H, m), 3.07 (4H, vbrs), 2.72 (2H, appd), 2.45 (2H, appt), 2.05-1.98 (2H, m), 1.80-1.63 (6H, m).

Example 9 N-[cis-4-(2,5-difluorophenyl)-4-(1H-pyrrol-1-ylsulfonyl)cyclohexyl]-1,1,1-trifluoromethanesulfonamide

A suspension of the product of Example 7 (50 mg) and manganese dioxide (100 mg) in benzene (5 ml) was refluxed for 6 h. The reaction mixture was cooled and filtered. The filtrate was evaporated in vacuo. Purification by column chromatography gave the title compound (26 mg, 52%) as a white solid. ¹H NMR (500 MHz, CDCl₃) 7.11-7.07 (1H, m), 7.02-6.96 (1H, m), 6.87-6.83 (1H, m), 6.60 (2H, brs), 6.22 (2H, brs), 5.95 (1H, brs), 3.80 (1H, brs), 2.70 (2H, brs), 2.47 (2H, appt), 2.06-2.04 (2H, m), 1.68-1.63 (2H, m).

Example 10 cis-1-(2,5-difluorophenyl)-N-propyl-4-{[(trifluoromethyl)sulfonyl]amino}cyclohexanesulfonamide

A solution of the product of Example 5 (320 mg) in toluene (10 ml) was treated at room temperature with NiCl₂(dppp) (140 mg) and DIBAL-H (8 equivalents) and stirred at room temperature for 2 h. The reaction mixture was quenched with water, extracted with ethyl acetate and purified by column chromatography to give the title compound (55 mg, 18%) as a white solid. ¹⁹F NMR (470 MHz, CDCl₃) −78, −113, −118.

Example 11 cis-N-allyl-1-(2,5-difluorophenyl)-4-{[(trifluoromethyl)sulfonyl]amino}cyclohexanesulfonamide

A solution of the product of Example 5 (250 mg) and zirconocene dichloride (150 mg) in THF (5 ml) was cooled to −78° C. and treated with butyllithium (3 equivalents). The reaction mixture was stirred for 10 minutes, then warmed to room temperature and stirred for 2 h. The reaction mixture was cooled to −78° C. and treated with 2N aqueous HCl. The reaction mixture was warmed to room temperature and diluted with ethyl acetate. The organic layer was separated, washed with NaHCO₃ solution and brine, dried (MgSO₄), filtered and evaporated in vacuo. Purification by column chromatography gave the title compound (65 mg, 28%) as a white solid. (¹⁹F NMR (470 MHz, CDCl₃) −78, −113, −117) and also the bis(de-allylated) byproduct as a white solid.

Example 12 cis-1-(2,5-difluorophenyl)-N-(3-methylbut-2-en-1-yl)-4-{[(trifluoromethyl)sulfonyl]amino}cyclohexanesulfonamide

The product from Example 11 (20 mg) was dissolved in 2-methyl-2-butene (10 ml) and DCM (2 ml). 1,3-Bis-(2,4,6-trimethylphenyl)-2-imidazolidinylidene)dichloro(phenylmethylene)-(tricyclohexylphosphine)ruthenium (10 mg) was added and the reaction mixture was refluxed for 30 mins. The reaction mixture was filtered through silica, washing with ether. The filtrate was evaporated. Purification by flash column chromatography gave the title compound (10 mg). ¹⁹F NMR (470 MHz, CDCl₃) −78.2, −113, −117.6.

Example 13 cis-1-(2,5-difluorophenyl)-N-(3-methylbutyl)-4-{[(trifluoromethyl)sulfonyl]amino}cyclohexanesulfonamide

The product of Example 12 (5 mg) and 5% Pd—C (5 mg) in ethyl acetate (5 ml) was hydrogenated at 50 psi for 2 h. The catalyst was removed by filtration and the organic solvent was removed by evaporation under reduced pressure to give the title compound (5 mg, 100%) as a white solid. ¹⁹F NMR (470 MHz, CDCl₃) −78, −113.2, −117.5.

Example 14 cis-1-(2,5-difluorophenyl)-N-(4,4,4-trifluorobutyl)-4-{[(trifluoromethyl)sulfonyl]amino}cyclohexanesulfonamide

A solution of the byproduct from Example 11, Cs₂CO₃, 4,4,4-trifluorobutyl iodide and DMF was stirred at room temperature for 3 days. Aqueous work up gave the title compound as a white solid.

Example 15 cis-1-(2,5-difluorophenyl)-N-(2E-butenyl)-4-{[(trifluoromethyl)sulfonyl]amino}cyclohexanesulfonamide

The product of Example 11 (20 mg) was dissolved in DCM (2 ml) in a sealed tube and treated with 2-trifluoromethyl propene (2 ml), containing about 3% of 2-propene. 1,3-Bis-(2,4,6-trimethylphenyl)-2-imidazolidinylidene)dichloro(phenylmethylene)-(tricyclohexylphosphine)ruthenium (2 mg) was added and the reaction mixture was stirred at room temperature for 72 h. The reaction mixture was filtered through silica, washing with ether. The filtrate was evaporated. Purification by flash column chromatography gave the title compound (10 mg). 

1. A compound according to formula I:

wherein n is 0, 1, 2 or 3; X represents H, halogen, CN, N₃, OH, OR¹, N(R²)₂, CO₂H, CO₂R¹, OCOR¹, CHO, COR¹, CON(R²)₂, OCON(R²)₂, SCN, SR¹, S(O)R¹, SO₂R¹, SO₂N(R²)₂, OSO₂N(R²)₂, NHCOR¹, NHCO₂R¹, NHCON(R²)₂, NHSO₂R¹ or NHSO₂N(R²)₂; R¹ represents CF₃ or C₁₋₆alkyl, C₂₋₆alkenyl, C₃₋₉cycloalkyl or C₃₋₆cycloalkylC₁₋₆alkyl, any of which may bear up to 2 substituents selected from halogen, CN, CF₃, OR³, aryloxy, COR³, CO₂R³, OCOR⁴, SO₂R⁴, N(R⁵)₂, and CON(R⁵)₂, or R¹ represents aryl, arylC₁₋₆alkyl, C-heterocyclyl or C-heterocyclylC₁₋₆alkyl; each R² independently represents H or C₁₋₆alkyl, C₂₋₆alkenyl, C₃₋₉cycloalkyl or C₃₋₆cycloalkylC₁₋₆alkyl, any of which may bear up to 2 substituents selected from halogen, CN, CF₃, OR³, COR³, CO₂R³, OCOR⁴, SO₂R⁴ and CON(R⁵)₂; or two R² groups together with a nitrogen atom to which they are mutually attached complete an N-heterocyclyl group; R³ represents H or C₁₋₄alkyl; R⁴ represents C₁₋₄alkyl; R⁵ represents H or C₁₋₄alkyl, or two R⁵ groups together with a nitrogen atom to which they are mutually attached complete an azetidine, pyrrolidine, piperidine, morpholine, thiomorpholine or thiomorpholine-1,1-dioxide ring; each R⁶ independently represents H, C₁₋₆alkyl, C₃₋₆cycloalkyl or C₂₋₆alkenyl, any of which is optionally substituted with up to 3 halogen atoms or with CN; or the two R⁶ groups and the nitrogen to which they are attached complete an N-heterocyclyl group or a heteroaryl group which is attached through N; Ar² represents phenyl or heteroaryl, either of which bears 0-3 substituents independently selected from halogen, CN, NO₂, CF₃, CHF₂, OH, OCF₃, CHO, CH═NOH, C₁₋₄alkoxy, C₁₋₄alkoxycarbonyl, C₂₋₆acyl, C₂₋₆alkenyl and C₁₋₄alkyl which optionally bears a substituent selected from halogen, CN, NO₂, CF₃, OH and C₁₋₄alkoxy; “aryl” at every occurrence thereof refers to phenyl or heteroaryl which optionally bear up to 3 substituents selected from halogen, CN, NO₂, CF₃, OCF₃, OH, COR³, CO₂R³, OCOR⁴, N(R⁵)₂, CON(R⁵)₂ and optionally-substituted C₁₋₆alkyl, C₁₋₆alkoxy, C₂₋₆alkenyl or C₂₋₆alkenyloxy wherein the substituent is selected from halogen, CN, CF₃, phenyl, OR³, CO₂R³, OCOR³a, N(R⁵)₂ and CON(R⁵)₂; and “C-heterocyclyl” and “N-heterocyclyl” at every occurrence thereof refer respectively to a heterocyclic ring system attached through carbon or nitrogen, said ring system being non-aromatic and comprising up to 10 atoms, at least one of which is O, N or S, and optionally bearing up to 3 substituents selected from oxo, halogen, CN, NO₂, CF₃, OCF₃, OR³, COR³, CO₂R³, OCOR⁴, OSO₂R⁴, N(R⁵)₂, CON(R⁵)₂ and optionally-substituted phenyl, C₁₋₆alkyl, C₁₋₆alkoxy, C₂₋₆alkenyl or C₂₋₆alkenyloxy wherein the substituent is selected from halogen, CN, CF₃, OR³, CO₂R³, OCOR⁴, N(R⁵)₂ and CON(R⁵)₂; or a pharmaceutically acceptable salt thereof.
 2. A compound according to claim 1 wherein n is 1 or 2 and X represents CN, N₃, OH, CO₂H, CO₂R¹, CON(R²)₂, SO₂R¹, SO₂N(R²)₂ or OSO₂N(R²)₂.
 3. A compound according to claim 2 wherein X represents CO₂H, CO₂R¹, CON(R²)₂, SO₂R¹ or SO₂N(R²)₂.
 4. A compound according to claim 1 wherein n is 0 and X represents NHCOR¹, NHCO₂R¹, NHCON(R²)₂, NHSO₂R¹ or NHSO₂N(R²)₂.
 5. A compound according to claim 4 wherein X represents NHSO₂R¹ or NHSO₂N(R²)₂.
 6. A compound according to claim 1 wherein R¹ represents CF₃ or an alkyl, cycloalkyl or cycloalkylalkyl group optionally substituted with halogen, CF₃, CN, OR³, COR³ CO₂R³ or CON(R⁵)₂.
 7. A compound according to claim 1 wherein R¹ represents aryl or arylalkyl optionally bearing up to 3 substituents selected from halogen, CF₃, OCF₃, C₁₋₆alkyl, OH and C₁₋₆alkoxy.
 8. A compound according to claim 1 wherein N(R²)₂ represents an azetidine, pyrrolidine, 3-pyrroline, piperidine, morpholine, thiomorpholine or 2-aza-5-oxabicyclo[2.2.1]heptane ring optionally substituted with oxo, halogen, CF₃, OR³, OCOR⁴, OSO₂R⁴, CO₂R³, N(R⁵)₂ or C₁₋₆alkyl.
 9. A compound according to claim 1 wherein the two R⁶ groups independently represent H, C₁₋₆alkyl, C₃₋₆cycloalkyl or C₂₋₆ alkenyl, any of which is optionally substituted with CN or up to 3 halogen atoms, provided that the R⁶ groups are not both H.
 10. A compound according to claim 1 wherein the two R⁶ groups complete a cyclic group selected from 4-fluoropiperidin-1-yl, 4,4-difluoropiperidin-1-yl, 4-(trifluoromethyl)piperidin-1-yl, pyrrolidin-1-yl, 3-pyrrolin-1-yl and pyrrol-1-yl.
 11. A compound according to claim 1 wherein Ar² represents 2,5-difluorophenyl and the other variables are as indicated in the following table: n X N(R⁶)₂ 0 NHSO₂CF₃ 4,4-di-F-piperidin-1-yl 0 NHSO₂CF₃ 4-CF₃-piperidin-1-yl 0 NHSO₂CF₃ diallylamino 0 NHSO₂CF₃ di(n-propyl)amino 0 NHSO₂CF₃ 3-pyrrolin-1-yl 0 NHSO₂CF₃ pyrrolidin-1-yl 0 NHSO₂CF₃ pyrrol-1-yl 0 NHSO₂CF₃ n-propylamino 0 NHSO₂CF₃ allylamino 0 NHSO₂CF₃ 3-methylbut-2-enylamino 0 NHSO₂CF₃ 3-methylbutylamino 0 NHSO₂CF₃ 4,4,4-trifluorobutylamino 0 NHSO₂CF₃ but-2-enylamino 0 H 4,4-di-F-piperidin-1-yl 0 H 4-CF₃-piperidin-1-yl 0 NHSO₂-(2-thienyl) 4-CF₃-piperidin-1-yl 1 CN 4,4-di-F-piperidin-1-yl 0 NHSO₂CF₃ 4-F-piperidin-1-yl 1 CONH₂ 4,4-di-F-piperidin-1-yl 1 CONHCH₂CH₂CF₃ 4,4-di-F-piperidin-1-yl 1 CONHCH₂CH₂F 4,4-di-F-piperidin-1-yl 0 NHSO₂CF₃ 3,3,3-trifluoropropylamino


12. A pharmaceutical composition comprising a compound of formula I as defined in claim 1, or a pharmaceutically acceptable salt thereof, and a pharmaceutically acceptable carrier.
 13. A method of treatment of a subject suffering from Alzheimer's disease which comprises administering to that subject an effective amount of a compound of formula I as defined in claim 1 or a pharmaceutically acceptable salt thereof. 